Compound metal stock



May 28, 1957 M. J. STUMBOCK COMPOUND METAL STOCK Filed April 19, 1954Fauna/0444140) A T'TORNE) 2,793,423 Patented May 28, 1957 COMPOUND METALSTOCK Max J. Stumbock, South Orange, N. J., assignor to Baker & Co.,Inc., Newark, N. 1., a corporation of New Jersey Application April 19,1954, Serial No. 423,956

5 Claims. (Cl. 29-194) The present invention deals with a compound metalstock and is concerned in particular with the provision of metal stockhaving a palladium alloy layer and a base metal backing.

In the manufacture of certain types of jewelry, watch cases, orpalladium-surfaced equipment, it is customary to use a compound metalhaving a relatively thin palladium layer combined with a base layer ofinexpensive metal. Base layers of brass, bronze, stainless steel, andGerman silver have been used for backings with palladium layers and theselection of such base metals has been largely dependent upon theparticular use for which the composite or compound metal is intended.However, it has been found that, as in the case of gold alloys, thepalladium develops a surface roughness upon annealing and working thecomposite metal for fabrication into palladium-clad articles orpalladium-clad equipment. The surface roughness is referred to in theart as orange peel roughness. In order to overcome this disadvantage theart, in the case of gold alloys, resorts to somewhat complicatedspecific quaternary alloys or alloys such that substantial additions ofbase metals, including metals of the iron group, are necessary topreclude grain growth. In the case of a compound metal stock consistingof a thin layer of palladium on a base metal backing, the addition ofany base metal of the iron group to the palladium does notsatisfactorily prevent grain growth since the grain size depends uponthe specific iron group metal used and more particularly to a specificrange of such base metals for the prevention of the orange peel defect.

When palladium composite stock is employed for jewelry purposes, thereis a limitation on the amount of base metals which may be legallyemployed. Usually the base metal content which would preclude the orangepeel defect exceeds such base metal limitation.

It is an object of the present invention to provide a compound metalstock consisting of a thin layer of a palladium alloy on a base metalbacking. It is another object of the present invention to provide acompound metal stock consisting of a palladium alloy on a base metalbacking, wherein the palladium alloy may be annealed and worked withoutdeleterious grain growth. Other objects of the present invention willbecome apparent from the description hereinafter following and thedrawing forming a part hereof.

The drawing illustrates a cross-sectional view of a compound metal stockaccording to the present invention.

The present invention deals with a compound metal stock consisting of athin layer of a binary palladium alloy on a base metal backing includingpreferably at least one of the backing metals brass, bronze, stainlesssteel, and German silver, wherein the palladium alloy after successiveannealing and working consists of grains ranging in size from 0.005 mm.to 0.035 mm. and preferably a major portion of such grains ranging below0.025

In forming a compound metal of the type contemplated by this invention,it is desirable to join the layers together before they are rolled totheir final thinness, whereby it is possible to obtain thinner layerswith a more suitable bond between the layers and with greater ease inhandling. After a relatively thick compound metal stock is thus formed,it is subjected to the usual mechanical processes of rolling, pressing,bending, etc. to obtain a final product having the desired shape. It iswell known, however, that when metals are so treated, they become hardand brittle and may not be further worked until they are again made softas by annealing. A complete forming and shaping process, therefore,usually comprises several successive steps of rolling and annealing,during which successive steps the metal becomes first hand and thensoft, there being a final annealing treatment after the reduced metalstock is bent or otherwise formed into the desired shape so that themetal will be in a durable, flexible and resilient condition. It isduring such successive steps of annealing and working that the orangepeel defect develops in the palladium alloy layer, unless the compoundstock consists of a layer of palladium alloy consisting of palladium andfrom 1% to 5% cobalt in accordance with this invention.

The cobalt content is quite critical in the maintaining of the alloygrain size below 0.035 mm. and, surprisingly the cobalt content in therange specified is more than twice as efficient as the next best metaltested for elimination of the orange peel defect. For example, the irongroup metal nickel which is widely used together with palladium as abinary alloy is only capable of maintaining less than one-half of thegrain sizes below 0.035 mm. Specifically, the alloy palladium with 4%nickel maintains about 50% of the grain sizes in the neighborhood of0.035 mm. On the other hand, in spite of the fact that nickel is closelyrelated to cobalt, the alloy palladium with 4% cobalt provides grainssuch that 45% thereof range from 0.005 mm. to 0.008 mm., 30% range from0.010 mm. to 0.015 mm., and 25% above 0.015 mm., but below 0.035 mm.With 5% cobalt, the optimum grain sizes are obtained since of such grainsizes are between 0.005 mm. and 0.10 mm. with 10% thereof being 0.015mm. in size.

Furthermore, it has been found that the palladium alloy consisting offrom 1% to 5% cobalt draws excellently and in a superior manner incomparison with the conventional palladium alloys, and the color of the5% cobalt-palladium alloy is a pleasing bluish white, which comparesfavorably with that of the well known platinum and white gold alloys notonly with respect to color characteristics but to oxidation andcorrosion resistance as well.

What I claim is:

1. A compound metal stock comprising a layer of palladium alloy on abase metal backing, said palladium alloy consisting of palladium andfrom 1% to 5% cobalt.

2. A compound metal stock comprising a layer of palladium alloy on abase metal backing, said backing consisting of at least one of themetals brass, bronze, stainless steel, and German silver, said palladiumalloy consisting of palladium and from 1% to 5% cobalt.

3. A compound metal stock comprising a layer of palladium alloy on abase metal backing, said palladium alloy consisting of 5% cobalt.

4. A compound metal stock comprising a layer of palladium alloy on abase metal backing, said palladium alloy consisting of palladium andfrom 1% to 5% cobalt, said alloy having grain sizes ranging between0.005 mm. to 0.035 mm. with the major portion of said grains rangingbelow 0.025 mm.

5. A compound metal stock according to claim 3, 2,105,312 Cohn Jan. 11,1938 wherein 90% 0f the grain sizes of said alloy are between 2,143,217Truths Jan. 10, 1939 0.005 mm. to 0.010 mm. and 10% below 0.025 mm,2,470,034 Hensel May 10, 1949 2,501,164 Durst Mar. 21, 1950 UNITEDSTATES PATENTS 5 2,539,096 Miller Jan. 23, 1951 References Cited in thefile of this patent 2,074,996 Cohn Mar. 23, 1937

1. A COMPOUND METAL STOCK COMPRISING A LAYER OF PALLADIUM ALLOY ON ABASE METAL BACKING, SAID PALLADIUM ALLOY CONSISTING OF PALLADIUM ANDFROM 1% TO 5% COBALT.